Volume-regulated chloride conductance in the LNCaP human prostate cancer cell line

Patch-clamp recordings were used to study ioncurrents induced by cell swelling caused by hypotonicity in humanprostate cancer epithelial cells, LNCaP. The reversal potential of the swelling-evoked current suggested that Cl was the primarycharge carrier (termed I_Cl,swell). Theselectivity sequence of the underlying volume-regulated anion channels(VRACs) for different anions wasBrI > Cl > F > methanesulfonate glutamate, with relativepermeability numbers of 1.26, 1.20, 1.0, 0.77, 0.49, and 0.036, respectively. The current-voltage patterns of the whole cell currentsas well as single-channel currents showed moderate outwardrectification. Unitary VRAC conductance was determined at 9.6 ± 1.8 pS. Conventional Cl channel blockers5-nitro-2-(3-phenylpropylamino)benzoic acid (100 µM) and DIDS (100 µM) inhibited whole cell I_Cl,swell in a voltage-dependent manner, with the block decreasing from 39.6 ± 9.7% and 71.0 ± 11.0% at +50 mV to 26.2 ± 7.2% and14.5 ± 6.6% at 100 mV, respectively. Verapamil (50 µM), astandard Ca²⁺ antagonist and P-glycoprotein functioninhibitor, depressed the current by a maximum of 15%. Protein tyrosinekinase inhibitors downregulated I_Cl,swell(genistein with an IC₅₀ of 2.6 µM and lavendustin A by60 ± 14% at 1 µM). The protein tyrosine phosphatase inhibitorsodium orthovanadate (500 µM) stimulatedI_Cl,swell by 54 ± 11%. We conclude thatVRACs in human prostate cancer epithelial cells are modulated viaprotein tyrosine phosphorylation.